Judge Watermeyer prefaced two rules with “As WATERMEYER JA said in Rex v Blom 1939 AD 188, there are two cardinal rules of logic which govern the use of circumstantial evidence in a criminal trial. At 202-203, the learned JUDGE OF APPEAL said:
“In reasoning by inference there are two cardinal rules of logic which cannot be ignored:
(1) The inference sought to be drawn must be consistent with all the proved facts. If it is not, the inference cannot be drawn.
(2) The proved facts should be such that they exclude every reasonable inference from them save the one sought to be drawn. If they do not exclude other reasonable inferences, then there must be a doubt whether the inference sought to be drawn is correct.”